1. Field of the Invention
The present invention relates to a cylindrical battery. More particularly, the present invention relates to a cylindrical battery configured to reduce or prevent the possibility of damage arising from externally-applied pressure.
2. Description of the Related Art
Generally, a conventional cylindrical battery may include an electrode assembly formed by winding internal components in a cylindrical shape, a can having a cylindrical shape into which the electrode assembly is inserted, electrolyte injected into the inside of the can for allowing ions to move, and a cap assembly combined with one end of the can to prevent leakage of the electrolyte and separation of the electrode assembly.
Conventional cylindrical batteries may have relatively high capacities, e.g., 2,000-2,400 mA in the case of a lithium ion secondary battery.
Accordingly, they may be installed in devices requiring a large power capacity, e.g., laptop computers, digital cameras, camcorders, etc. For example, a desired number of batteries may be connected in series or parallel, or assembled in a hard pack with a protection circuit to be used as a power supply of the aforementioned electronic devices.
Fabricating a conventional cylindrical battery may include the following operations. First, a negative electrode plate, on which a predetermined activation material layer is formed, a separator, and a positive electrode plate, on which a predetermined activation material layer is formed, may be stacked together. Then, the stack may be combined with a winding axis having a bar shape and wound in a cylindrical shape, thereby forming an electrode assembly. The electrode assembly may be inserted into a cylindrical can, and electrolyte may then be injected. A cap assembly may be welded to the upper portion of the cylindrical can, thereby completing the battery.
In order to prevent deformation of the electrode assembly during charging/discharging the battery, a tubular center pin may be disposed in the center of the electrode assembly. However, the center pin may be deformed or broken down by external pressure. If the center pin is deformed or broken down, the separator in the electrode assembly may also be broken down. This may result in a defect of the separator, which may generate a short circuit between the positive and negative electrode plates and may lead to battery failure or explosion. If the center pin is deformed by external pressure, particularly, lengthwise pressure, the cross-sectional contour of the tubular center pin may become deformed and uneven. Such unevenness of the cross-sectional contour may generate critical breakdowns of the separator.